Isoelastic flexure suspended and driven gyros



1961 R. K. BRODERSEN ETAL 2,995,938

ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Filed July 15, 1960 6 Sheets-Sheet l lHlHllHl POZF K 55005550 IN V EN TORS Aug. 15, 1961 R. K. BRODERSEN ET AL 2,995,938

ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Filed July 13, 1960 6 SheetsSheet 2 E01 F K. 5POD5ON EED D. L/ T T Y 1N VEN TOR5 ATTOP/VEY' Aug. 15, 1961 R. K. BRODERSEN ETAL 2,995,933

ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Filed July 13, 1960 6 Sheets-Sheet 3 e00 K. BRODfESO/V FEED 0. L/7'7'7 INVENTORS 1961 R. K. BRODERSEN ETAL 2,995,938

ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Filed July 15, 1960 e Sheets-Sheet 4 W W a Q Ow L INVENTORS 1961 R. K. BRODERSEN ETAL 2,995,938

ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Filed July 13, 1960 6 Sheets-Sheet 5 (d) D/AMETEQ f 25.6 Z/-/ .35 2&0 24/ 20,5 25 L .040 .0@& .055 .090 .535 ./00 24 25 22 2/ 20 i I l l l 0 .020 ,040 .04 0.oa0./a0./20

Ralf K 519005950 FEED D. L/TT) INVENTORS United States Patent 2,995,938 ISOELASTIC FLEXURE SUSPENDED AND DRIVEN GYROS Rolf K. Brodersen, Orange, and Fred D. Litty, Towaco,

N.J., assignors to General Precision Inc., Little Falls,

N.J., a corporation of Delaware Filed July 13, 1960, Ser. No. 42,717 12 Claims. (Cl. 745.7)

This invention generally relates to improvements in flexure suspended and driven gyroscopes and more particularly to gyroscopes having two-degrees-of-freedorn which are provided by means of a magnetically compensated flexure suspension.

In a prior application Serial No. 838,979, filed September 9, 1959, directed to a Pivot Spring Suspended Gyro and assigned to the same assignee, there is disclosed an improved gyro construction that eliminates the use of conventional gimbals and bearings or pivot-type movable joints and substitutes instead a deflectable solid spring flexure member that is compensated to minimize unbalances and undesired spring return forces and torques. This construction considerably simplifies the manufacture of the gyro and, quite importantly, markedly reduces or eliminates many types of gyro errors that are inherently associated with bearings and other known prior art pivots.

According to the present invention there is provided improvements in the construction of both the flexure pivot and deflection means and in the magnetic compensating means for the flexure suspension, which improvements are directed toward rendering the gyro more sensitive and reliable and otherwise improving its performance.

It is, accordingly, a principal object of the invention to provide an improved flexure suspended gyro having an isoelastic flexure joint coupled with a supplementary angular deflection member, whereby the gyro responds uniformly to displacement about all sensitive axes.

A further object is to provide such a gyro having increased sensitivity about all sensitive axes.

A primary feature is the isoelasticity of the flexure mechanism, in that the degree of flexibility is substantially equal in three directions.

A still further object is to provide such a gyro having an improved magnetic compensating means for the spring flexure.

Other objects and many additional advantages will be more readily understood by those skilled in the art after a detailed consideration of the following specification, taken with the accompanying drawings wherein:

FIGURE 1 is a vertical sectional view illustrating a preferred dual spring flexure and flywheel construction for use in a gyro;

FIGURE 2 is a partial vertical section illustrating a similar flywheel and multiple spring flexure embodied in a gyroscope construction;

FIGURE 3 is a cross-sectional view taken through lines 33 of FIGURE 2;

FIGURE 4 is a vertical sectional view illustrating another embodiment of the invention;

FIGURE 5 is a cross-sectional view similar to FIG- URES 2 and 4, and illustrating further features of the invention;

FIGURES 6 and 7 are plotted graphs illustrating the preferred relationships between the flexure and flywheel dimensions and the operational characteristics of these elements; and

FIGURE 8 is a vertical section, similar to FIGURE 4, through a modification of the construction shown in FIG- URE 4, the section being taken on the line 88 of FIG- URE 9;

FIGURE 9 is a plan view of the construction shown in FIGURE 8, with the flywheel removed, the view being taken on the line 99, FIGURE 8.

FIGURE 10 is a schematic wiring diagram of the coils and related portions of the apparatus shown in FIGURES 8 and 9.

Referring now to the drawings for a detailed consideration of the invention, there is shown, in FIGURE 1, one preferred construction of the flywheel 10 and flexure 11 for the gyro. As shown, the flywheel 10, solid flexure portion 11, and drive shaft portion 12 are all preferably formed as an integral and symmetrical unit about the central or spin axis 13 passing lengthwise through the members.

The function of the solid flexure portion 11 is to provide a positive rotative drive connection between the drive shaft 12 and flywheel 10, but to permit flexing or pivoting action therebetween about all coordinate axes perpendicular to spin axis 13. Consequently, when the rather large and heavy flywheel 10 is being rotated at high speed by the drive shaft 12, it serves as an effective gyroscope rotor tending to maintain its same orientation in space despite pivoting or tilting of the drive shaft 12. Any such tilting or pivoting of shaft 12, about any axis transverse to spin axis 13, merely serves to flex or bend the cylindrical flexure portion 11 about that axis, thereby providing a universally pivotable joint between the flywheel 10 and drive shaft '12.

According to the present invention the construction of the solid flexure portion 11 and flywheel 10 is such as to provide an isoelastic joint between the members provid ing a high bending compliance therebetween that is equal about all axes transverse to the spin axis 13. To provide such a joint, it is also necessary that the axial compliance in a direction parallel to or in substantial alignment with axis 13 and the radial compliance in a direction transverse to axis 13 also be made equal to one another. In other words, the construction is such as to provide, not only uniform pivoting deflection about axis 13 by means of bending of the solid cylindrical flexure portion 11, but also to provide equal radial and axial deflections (transverse to axis 13 and parallel to axis 13, respectively) for equal radial and axial forces being exerted upon the flywheel and the solid cylindrical flexure portion 11. The deflection relative to a plane perpendicular to the axis 13, is provided by the thin dished flexure portion.

To provide this desired function the flywheel 10 is preferably formed in a flexible dished washer-type configuration having a relatively thin central flexure portion 14 extending radially outward and being inclined slightly upwardly from the central hub portion 15 of the flywheel. The outer rim portion 16 of the flywheel 10 is, in turn, formed of a considerably thicker wall section than the central dished flexure portion 14 to not only concentrate the weight of the flywheel about the periphery thereof, as is desired, but also to provide a substantially rigid outer ring. With this construction, the central dished flexure portion 14 of the flywheel is relatively flexible and will yield or comply in response to axially directed forces operating parallel to the spin axis 13. Thus, by suitably dimensioning the thickness of the central dished flexure portion 14 to provide the desired flexibility to axial forces with the diameter and length of the solid cylindrical flexure portion 11, an isoelastic joint may be provided which has low and equal radial and axial compliance while providing a high compliance in bending uniformly about the solid cylindrical flexure portion 11.

FIGURE 2 illustrates one preferred gyro structure employing the isoelastic joint construct-ion of FIGURE 1. As shown, the gyro is composed of an outer housing, generally indicated at 18, within which is contained the integrally formed drive shaft portion 19, solid flexure portion 20 and which is integral with the shaft portion 19,

and flywheel portion 21 which is integral with, or supported by, the shaft portion 19, all being normal-1y rotatable about spin axis 22.

The flywheel portion 21 is in an inverted cup-shaped form having a relatively massive outer rim 23 depending downward about its periphery and being connected to the hub portion 24 by means of a relatively thin-walled central flexure portion 25, which flexure wall is suificiently thin in relation to the diameter and length of the solid flexure 20 to permit axial compliance or limited deflection in response to axial forces directed lengthwise along spin axis 22. The walls of the central portion are also inclined in a direction slightly upwardly from the cylindrical hub 24, as shown, thereby to resemble in function, a flexible dished washer construction as discussed above in connection with FIGURE 1.

For spinning the flywheel at the high speed desired, an electrical, or other type of drive motor (not shown), may be located either within or outside the housing 18, which drive motor is connected to drive shaft 19, thereby rotating the shaft 19 and the flywheel in synchronism through the solid cylindrical flexure portion 20.

When the flywheel 21 is being rotated at high speed, it serves as an effective gyroscope tending to maintain its same orientation in space despite tilting or pivoting of the housing 18 about any axis perpendicular to or aligned with the normally vertical axis 22. Any such tilting or deflection of the housing 18 merely serves to flex the solid cylindrical flexure portion, thereby providing a universally pivotable joint between the flywheel and the housing, the limits of such flexure being, of course, determined by the clearances existing between the outer surface of the flywheel and the adjoining portions of the housing or the members attached to the interior thereof. Pickotf means are provided for producing an electrical signal proportional to the deflection between the flywheel and housing and torque producing means are provided for precessing the flywheel spin axis as desired. Such means are generally indicated as elements 26 and 27 in FIGURE 2, having portions supported inside the housing and being adapted to cooperate with the outer portion of the flywheel rim 23.

The solid cylindrical flexure portion 20 operates as a spring and provides a restoring torque in such direction as to oppose any displacement between the flywheel 21 and housing 18. To compensate for this spring force, there is provided one or more permanent magnet members 28 which is supported on a series of arms or a circular disc 29, which disc is positioned underneath the flywheel 21 and connected to the drive shaft 19 to rotate with the flywheel.

The magnet 28 which is in the form of a heavy walled tubular permanent magnet is located under the flywheel and consequently exerts no unbalanced force upon the flywheel when the flywheel and housing are in alignment, a shown in FIGURE 2. However, upon relative deflection between the flywheel and housing, the magnet exerts a net attracting force tending to increase the deflection and this force is designed to be equal and opposite the spring return force being exerted by the solid cylindrical flexure 20 and the dished central flexure portion 25. Consequently, the magnet provides compensation for the solid cylindrical flexure 20 and the dished central flexure portion 25, to insure a substantially neutral universal suspension of the flywheel as desired.

The combination of the small cylindrical flexure 20, and the central dished flexure port-ion 25 integral with the flywheel, provides isoelasticity of the unit, in that it provides, a substantially equal degree of flexibility in three directions,- relative to the normally vertical axis of the drive shaft 19.

Due to the relative movement between the gyro flywheel 21 and the permanent magnet 28 upon deflection of the flywheel 21, eddy currents may be produced in the flywheel 21 and in the magnet supporting disc 29 as well as in other portions of the gyro structure in the vicinity of the magnetic lines of force. Under certain conditions such eddy currents may produce undesired torques operating upon the flywheel 21 and tending to displace or unbalance the flywheel from its proper axis.

In FIGURES 4 and 5 there are shown in diagrammatic form, preferred means for minimizing the eddy current effects. In principle, the means employed for reducing the effect and magnitude of the eddy currents being produced is to construct all portions of the gyro that are subjected to the magnetic field, of 'a high electrical resistance material such as a ferrite composition or a laminated metal layer construction. Thus the flywheel 35, in FIGURE 4, is constructed of a composite number of materials, with the hub portion 36 being of steel or other material as in FIGURES l to 3, and next a central ring insulator 37 of ceramic material or the like, concentrically about which is placed the extended wall top portion 38 of the flywheel which is made of a ferrite composition or other high resistivity material. This central top portion is acted upon by the magnetic field and hence the high resistivity material markedly reduces the amplitude of the eddy currents being generated. Completing the flywheel 35, the central wall portion 38 is, in turn, banded by an insulating ring 39 of ceramic or other non-conductor which is finally encircled by the outer massive rim 40 which is made of a ceramic material, or other suitable material. In a similar manner the cylindrical disc type magnet 41 is also carried by a composite support comprised of high electrical resistivity material and insulators whereby all portions of the gyro being subjected to the magnetic field are so constructed as to minimize eddy current flow. Specificahy, in the preferred embodiment shown, the shallow cylindrical magnet 41 is carried on a flat cylindrical disc 42 of high resistivity material such as a ferrite which is connected to the drive shaft 47 by a tubular non-conducting band 43 made of a ceramic material, or other suitable material, the tubular band 43 also separating the permanent magnet 41 from the shaft 47. A second non-conducting ring 44 encircles the opposite upright side of the mag nets, followed by a concentric ring 45 of a high resistivity ferrite or the like and finally by a laminated or tape wound retaining ring 46 that maintains the magnet assembly together.

The flexure member shown in FIGURE 4, comprises a substantially cylindrical upper body section 72, which is pressed into, or otherwise attached to the hub portion 36, a reduced diameter cylindrical flexure portion 73, integral with the upper body, and a cylindrical lower body section 74, which is pressed into, or otherwise attached to the upper hub of the drive shaft 47, as shown in FIGURE 4.

A shoulder or collar may be formed integral with each of the cylindrical body sections 72, 74 of the flexure member, to locate the body sections relative to the respective hub portions 36, 47.

FIGURE 5 illustrates an alternative embodiment of the invention that is similar to that of FIGURE 2 but also including an eddy current control device, similar to that shown in FIGURE 4. In this construction a composite flywheel 50 is introduced, the flexure section 48 of the head of the flywheel being supported from the base thereof, which is located close to the permanent magnet disc. This phase of the construction is similar to the inclined wall or dished portion 25 of FIGURE 2 or 14 of FIGURE 1, which latter constructions are of the dished flexible washer type, as discussed above. In the construction of FIGURE 5, the axial compliance of deflection in response to unit force of this flat wall has been found by calculation to be about one third of the compliance obtainable with the flexible dished washer type construction and consequently may be desired in the larger gyros employing a larger diameter solid cylindrical flexure 20 and providing a low radial compliance in response to transversely directed forces. In operation, the joint functions in essentially the same manner as does that of FIGURES 1 and 2, in providing an isoelastic joint wherein the bending torques and transverse forces are taken by deflection of the solid cylindrical flexure 20 and the axial forces are taken by deflection of the thin central wall portion 48 of the flywheel 50.

FIGURE 5 also illustrates an alternative construction and arrangement of the compensating magnet 51 and further details of the motor drive and bearings for the drive shaft 71. As shown, the compensating magnet 51 may be supported on a composite disc 49 underneath the depending rim, which is attached to and aligned with the bottom of the rim portion 23 of the flywheel 50 rather than under the central thin wall section 25 of FIG- URE 2. This arrangement enables the relatively flexible portion of the wall section to be extended beyond that obtainable in the construction of FIGURE 2.

In order to compensate for the eddy currents in a manner similar to FIGURE 4, and still maintain a central dished flexure 48 similar to that shown in FIGURE 1, the flywheel 50 is formed of a composite construction, the head construction and the rim 23 thereof being similar to those shown in FIGURE 1.

The annular base 52 of the flywheel, is substantially parallel to the disc type permanent magnet 51, the base disc being fixedly attached to and isolated from the rim 23 of the flywheel by a ring 53, which is formed of a non-conducting or ceramic material, the ring being inserted in a counter-bore in the rim 23 of the flywheel, The permanent magnet 51 is supported by a composite disc 49, which is in turn attached to the cylindrical portion of the shaft 19. The circular disc type permanent magiet 51 is carried by a composite support disc 49 which is basically formed of a composite consisting of electrical high resistivity materials, and insulators, in a manner similar to that shown in FIGURE 4, so that all portions of the gyro subjected to the magnetic field, are so constructed as to minimize eddy current flow. "the permanent magnet 51 is carried on a flat circular disc 49a, of a high resistivity material, such as a ferrite, which is supported on the drive shaft 19 by a tubular nonconducting bushing or ring 66, which is made of a ceramic material, the ring 66 extending upward into the inner diameter of the permanent magnet 51. A second non-conducting ring 67, which is also made of a ceramic material, surrounds the outer diameter of the permanent magnet 53, the second ring 67 being supported by the circular disc 4%. An outer ring 68, of a ferrite or other electrical high resistivity material, surrounds the outer circumference of the disc 49a, and the ring 67, a laminated or tape wound retaining ring 69, being wrapped around the outer ring 68, to grip and retain the magnet and disc assembly in the relation shown in FIGURE 5 As further shown in FIGURE 5, the drive shaft 19 is rotatably supported in the housing 18 by means of large and durable anti-friction bearings 70, 70a. If the motor (not shown) is to be supported outside of the housing 18, the drive shaft may project outside the housing to engage with or be formed integrally with the motor shaft 71.

For a more vigorous explanation of the construction and design of the preferred isoelastic joint, reference is made to the formulae and explanation and to FIGURES 6 and 7 illustrating a plot of the construction criteria.

The radial compliance C of the flexure joint 20 consists of two parts; that due to shear compliance C and that due to double bending C The total radial compliance C in terms of the length (L) and diameter (d) of the solid cylindrical flexure is:

i: 64L M EH1 The ratio of radial compliance C to bendingcompliance C should be as low as possible to provide the gyro with the maximum sensitivity to tilting displacement about its sensitive axis and a minimum sensitivity to disturbances by a transverse translation force. However, the limiting factors in the construction of the diameter and diameterto-length ratio for the solid cylindrical flexure 20 are manufacturing limitations on the size of these dimensions, sufficient strength to withstand fatigue stress and compatibility of the total radial and axial compliances.

In FIGURE 6 there is shown a plot of the ratio of radial compliance to moment compliance as the ordinate and the diameter of the solid cylindrical flexure 20 as the abscissa with the upright line 56 establishing the minimum diameter to be determined in accordance with factors such as fatigue stress, manufacturing limitations, and others as mentioned above. The three solid line curves 57, 58, and 59 indicate the variation in this compliance ratio for flexures of diiferent length. Since it is desired to provide the maximum bending compliance and the minimum radial compliance, the ratio should be as low as possible; and on the basis of this criteria alone one would select the length L as being preferred.

However, consideration of the spring rate of the flexure joint in bending to the permissible radial load or:

M/0 new Ed F 1rS, max d iS' max L indicate that this latter ratio should also be as low as possible and dotted line curves 60, 61, and 62, in FIG- URE 6, wherein this latter ratio is plotted for given lengths indicate that length L is inferior to- L in this characteristic.

To obtain the optimum length for a minimum diameter of the cylindrical flexure 20, the product of these two functions is plotted as the ordinate in FIGURE 7 as against length and the minimum value of the curve 63 being obtained gives the optimum length of the flexure desired.

After this calculation has been completed it is then necessary to compute the radial compliance of a cylindrical flexure of the length and diameter selected and to equate this compliance with the axial compliance of the flywheel thin wall flexure section.

Computation has shown that the axial compliance of a free flexible dished washer of a given size and thickness of material is 1.377 1O" inches per pound, whereas that for a flat plate of the same size and material thickness rigidly constrained at its edges is much lower or .419X l0 inches per pound. Consequently the ultimate (length selected for the solid cylindrical flexure 20 of minimum diameter will he that length that yields the same radial compliance as the axial compliance of the flywheel, thereby to provide the isoelastic joint desired.

FIGURES 8 and 9 show a modification of the construction, shown in FIGURE 4, in which a plurality of coils laid in radial slots through the magnet are provided to adjust the spring rate compensation of the apparatus.

In this construction, a ring type permanent magnet 75 is provided under and substantially parallel to the substantially cylindrical flywheel 76, which is located above and substantially parallel to the permanent magnet 75. The upper portion of the permanent magnet is divided into six segments 77, 77a, 77b, by a plurality of equallyspaced radial slots 78, 78a, of substantially rectangular cross-section, as shown in FIGURE 9.

A coil 79, 79a, 80, 80a is wrapped around each of the magnet segments, the straight side sections 8 1, 82 of adjoining pairs of coils being embedded in each of the slots 78, 78a as shown in FIGURE 9.

The circuitry used to energize the coils 79, 80 is shown in FIGURE 10 and hereinafter described.

The flywheel 76 which is in the form of a relatively flat disc having a central opening therethrough, is supported by a hollow cylindrical hub 83 having a central cavity therethrough, the necked flexure pivot 84 being attached to the solid portion of the hub in a manner similar to that shown in FIGURE 4.

A cylindrical shaft section 85, integral with or fixedly attached to the flexure pivot 84 is mounted below the flexure pivot, the shaft supporting the magnet support member.

A hollow dished support member 86, made of steel or other suitable material, is fixedly attached to or integral with the shaft, the flat base 87 integral with the support member having a circular rim 88 integral therewith and perpendicular thereto, the rim surrounding the return path structure, on which the permanent magnet is supported.

The permanent magnet 75 is supported by a circular ferrite disc 90, which rests on the base 87 of the support member, the disc 90 and a ferrite ring 91, which surrounds the disc 90 and is fitted to the inner surface of the annular rim 88 of the support member serving as a return path for the magnetic flux of the permanent magnet.

The circular segmental inner and outer portions of the coils 79, 80, surround the circular segmental inner and outer surfaces of the magnet segments 77 to 77a in the manner shown in FIGURES 8 and 9.

As shown in the wiring circuit, FIGURE 10, two coils 79-792, and StL-Stle are fitted to each of the segments 77-77e of the permanent magnet 75.

Coils 79-79e provide fine adjustment of compensation. The induced voltages due to the deflection of the flywheel 75 cancel it the voltage through all the coils is equal.

Coils Sii-fitle provide 3 high point adjustments and need less power than the coils 79-79e. The induced voltages, which are generally less than 0.1 volt, and which are due to the deflection of the flywheel 76 will generate eddy currents. A excitation voltage is therefore desirable, and a high circuit impedance at the frequency of the induced voltage is required.

Four slip rings 93 and 94-941) provide excitation to the two groups of coils 79, 80, one slip ring being connected to one group of coils 79-79e, the other slip rings each being selectively connected to two of the coils 80-802. Thus, one slip ring 94 is connected to coils 80, 80a, the second to coils 86b, 80c, and the third to coils 80d, 80e.

The voltage for one slip ring 93 is supplied by a 500 volt D.C. torquer power supply 95 through a variable resistor 96.

The second group of slip rings receive their voltage from a second 500 Volt DC. torquer power supply 98, through a series of three variable resistors 99, 99a, 99b, each of which is connected to one of the slip rings 94, 94a, 94b.

The electrical compensation adjustment, herein described, is used to replace mechanical fine adjustment of compensation and high points as by the use of shims, shunt screws, and the like, which tend to contribute to instability, by substituting electrical trimming, using available power supplies. Usually coarse mechanical compensation adjustment will precede the electrical trimming.

In the wiring diagram, shown in FIGURE 10, if the circuit impedance can be kept high enough to make eddy current effects negligible, coils 79-792 and the corresponding slip ring 93 can be eliminated. Coils Sit-Site and the corresponding slip rings 94-9415 can then provide all the adjustments necessary.

What is claimed is:

1. In an astatic gyro having a symmetrical mass being rotatably driven about its central axis through a central shaft having a universally flexible solid substantially cylindrical spring flexure member integral therewith, and magnetic means operating upon said mass to compensate forsaid spring flexure member, the improvement in said 8 V gyro comprising the provision of a unitary flexure and mass with the mass being shaped in a substantially dished flexible washer configuration leading from one end of the shaft.

2. In the gyro of claim 1, said mass being comprised of a relatively thin wall and flexible central portion radially extending from its central axis and integral therewith, and thick-walled portions about its periphery.

3. In an astatic gyro having a symmetrical flywheel being rotatably driven about its central axis by a shaft, through a universally deflectable solid cylindrical flexure member, said flexure member and shaft supporting the flywheel being formed of a unitary material, said flywheel having a thin-walled and flexible central portion and a thick-walled inflexible peripheral portion and the solid cylindrical flexure member being of related length and thickness thereto to provide an isoelastic joint having equal radial and axial compliance and high bending compliance, permanent magnetic means rotatable in synchronism with said flywheel and proximate to said flywheel, said permanent magnetic means being supported by a member of high electrical resistivity material adjacent said magnetic means to reduce eddy current flow, and the portions of the flywheel proximate said permanent magnetic means and co-acting therewith, being of high electrical resistivity material.

4. In the gyro of claim 3, said high resistivity material being a ferrite composition.

5. In the gyro of claim 3, said high resistivity material being a laminated ferrite composition material.

6. A spring flexure gyro comprising a drive motor, a flywheel, and a universal solid substantially cylindrical spring flexure member integral with a shaft, centrally connecting the flywheel for rotation by the motor, permanent magnetic means rotatable by the motor and exerting a balanced force upon the flywheel in the absence of deflection of the solid cylindrical flexure member and an unbalanced force thereon substantially equal and opposite to the flexure spring return force upon deflection of the flexure member, the shaft supporting said flywheel and the flexure member being integrally formed and said flywheel having a central thin Walled flexure portion that is flexible and thicker outer peripheral wall portions that are rigidly constructed to provide with said solid cylindrical flexure member an isoelastic flexure joint providing equal radial and axial compliance and a high bending compliance that is equal in all radial directions, and means for reducing the generation of eddy currents in the gyro by reason of movement between the permanent magnetic means and the flywheel.

7. In the gyro of claim 6, said thin-walled flexure portion of said flywheel being formed in a substantially dished washer configuration and said eddy current reducing means being comprised of a supporting means for said permanent magnetic means being of a high resistivity material and portions of said flywheel exposed to the magnetic field of said permanent magnet being of high resistivity material.

8. In a two axis gyro having a flywheel centrally supported and rotatably driven by a solid substantially cylindrical spring flexure coaxial with the axis of rotation of the flywheel, magnetic means rotatably driven in synchronism with the flywheel and exerting an unbalanced force thereon during deflection of said cylindrical flexure and in opposition to said cylindrical flexure, supporting means for said magnetic means including portions adjoining said magnetic means being of high resistivity material to reduce eddy current flow, and portions of said flywheel acted upon by said magneticmeans being comprised of high resistivity material, thereby to reduce spurious torques as occasioned by eddy current flow.

9. In the gyro of claim 8, said high resistivity material being formed of a ferrite composition.

9 10 10. In the gyro of claim 8, said high resistivity material tially equal to the compliance transverse of the axis of being formed of a laminated ferrite material said cylindrical flexure.

11. In the gyro of claim 8, said flywheel with thin flexible portions and solid cylindrical flexure member References Cited m we file of this patent providing an isoelastic joint having substantially equal 5 UNITED STATES PATENTS and axial compliance and high bending compli nce uni- 1,192,532 Klahn July 25, 1916 versally about the flexure axis. 1,639,233 Paxton Aug. 16, 1927 12. In the gyro of claim 11, Said flywheel and cylindri- 2,852,943 Sedgfield Sept. 23, 1958 cal flexure being integrally formed and the thin-Walled 2,919,585 Schroeder Ian. 5, 1960 flexure portion of said flywheel being in a substantially 10 FOREIGN PATENTS dished washer configuration providing axial compliance along the axis of the cylindrical flexure that is substan- 509,447 France 1920 

